Wireless IC device

ABSTRACT

A wireless IC device includes a wireless IC chip arranged to process a radio signal, a power-supply circuit board that is connected to the wireless IC chip and that includes a power supply circuit including at least one coil pattern, and a radiation plate arranged to radiate a transmission signal supplied from the power-supply circuit board and/or receiving a reception signal to supply the reception signal to the power-supply circuit board. The radiation plate includes an opening provided in a portion thereof and a slit connected to the opening. When viewed in plan from the direction of the winding axis of the coil pattern, the opening in the radiation plate overlaps with an inner area of the coil pattern and the area of the inner area is approximately the same as that of opening.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to wireless integrated circuit (IC)devices including wireless ICs and radiation plates. More particularly,the present invention relates to a wireless IC device used in a radiofrequency identification (RFID) system.

2. Description of the Related Art

RFID systems have been developed as article management systems in recentyears. In such a RFID system, a reader-writer that generates an inducedmagnetic field communicates with an IC tag (hereinafter referred to as awireless IC device) that is attached to an article and that storesinformation by a non-contact method using the electromagnetic field totransfer information.

The wireless IC device used in an RFID system includes a wireless ICchip arranged to process a specific radio signal and a radiation platearranged to transmit and receive the radio signal. For example, a knownwireless IC device is described in WO 2007/083574.

The wireless IC device described in WO 2007/083574 includes a wirelessIC chip, a power-supply circuit board on which the wireless IC chip ismounted and which includes a power supply circuit including a resonantcircuit having a desired resonant frequency, and a radiation plate whichis adhered to a bottom surface of the power-supply circuit board andwhich radiates a transmission signal supplied from the power supplycircuit and receives a reception signal to supply the received receptionsignal to the power supply circuit. The resonant frequency of theresonant circuit in the power-supply circuit board is designed so as tosubstantially correspond to the frequency of the transmission andreception signals, such that the wireless IC device has very stablefrequency characteristics.

Since the frequency of the radio signal transmitted and received by theradiation plate is substantially determined by the power supply circuitin the power-supply circuit board in the wireless IC device described inWO 2007/083574, the wireless IC device has very good characteristics inthat the frequency of the radio signal does not significantly depend onthe size and/or shape of the radiation plate. However, for example, asdescribed in Paragraph [0020] in WO 2007/083574, the magnitude of thegain of the radio signal depends on the size and/or shape of theradiation plate. In other words, the gain varies depending on the sizeand/or shape of the radiation plate. However, a satisfactoryconfiguration for successfully controlling the gain is not disclosed inWO 2007/083574.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide a wireless IC device which effectivelycontrols the gain of transmission and reception signals.

A wireless IC device according to a preferred embodiment of the presentinvention includes a wireless IC arranged to process a specific radiosignal, a power-supply circuit board that is connected to the wirelessIC and that includes a power supply circuit including at least one coilpattern, and a radiation plate arranged to radiate a transmission signalsupplied from the power-supply circuit board and/or to receive areception signal to supply the reception signal to the power-supplycircuit board. The radiation plate includes an opening provided in aportion thereof and a slit connected to the opening and, when viewed inplan from the direction of the winding axis of the coil pattern, theopening in the radiation plate overlaps with at least a portion of aninner area of the coil pattern.

In the wireless IC device according to a preferred embodiment of thepresent invention, the radiation plate preferably includes the openingprovided in a portion thereof and the slit connected to the opening and,when viewed in plan from the direction of the winding axis of the coilpattern in the power-supply circuit board, the opening in the radiationplate overlaps with at least a portion of an inner area of the coilpattern. Accordingly, when a current flows through the coil pattern, amagnetic field that is excited is ideally distributed through theopening in the coil pattern. The induced magnetic field excites aninduced current around the opening in the radiation plate and adifference in voltage is applied to the induced current in the slit.Accordingly, the amount and/or distribution of the induced current canbe controlled by changing the length and/or width of the slit so as tocontrol the amounts of the electric field and the magnetic fieldoccurring over the radiation plate, thus enable effective control of thegain of the transmission and reception signals.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C include diagrams showing a wireless IC device accordingto a first preferred embodiment of the present invention wherein FIG. 1Ais a perspective view of the entire device, FIG. 1B is a perspectiveview showing a state in which a wireless IC chip is mounted on apower-supply circuit board, and FIG. 1C is a perspective view showing astate in which the power-supply circuit board is mounted on a radiationplate.

FIG. 2 is a plan view showing the wireless IC device of the firstpreferred embodiment of the present invention.

FIG. 3 is a schematic plan view showing a main portion of the wirelessIC device of the first preferred embodiment of the present invention.

FIG. 4 is a schematic perspective view showing the internalconfiguration of the power-supply circuit board included in the wirelessIC device of the first preferred embodiment of the present invention.

FIGS. 5A to 5C include diagrams showing the principle of the operationof the wireless IC device of the first preferred embodiment of thepresent invention wherein FIG. 5A is a cross-sectional view, FIG. 5B isa plan view around an opening, and FIG. 5C is a plan view showingpropagation to the radiation plate.

FIG. 6 is an equivalent circuit of the wireless IC device of the firstpreferred embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing a main portion of thewireless IC device of the first preferred embodiment of the presentinvention.

FIGS. 8A and 8B include diagrams showing a wireless IC device of asecond preferred embodiment of the present invention wherein FIG. 8A isa plan view and FIG. 8B is an enlarged plan view of a modification ofthe second preferred embodiment of the present invention.

FIG. 9 is a schematic perspective view showing a modification of a coilpattern provided inside the power-supply circuit board.

FIG. 10 is a cross-sectional view showing a wireless IC device of athird preferred embodiment of the present invention.

FIG. 11 is a plan view showing a wireless IC device, with thepower-supply circuit board omitted, of a fourth preferred embodiment ofthe present invention.

FIG. 12 is a plan view showing a wireless IC device, with thepower-supply circuit board omitted, of a fifth preferred embodiment ofthe present invention.

FIG. 13 is a front view showing a state in which the wireless IC deviceof the fifth preferred embodiment of the present invention is attachedto an article.

FIG. 14 is a perspective view showing a main portion of a wireless ICdevice of a sixth preferred embodiment of the present invention.

FIG. 15 is a cross-sectional view showing the wireless IC device of thesixth preferred embodiment of the present invention.

FIG. 16 is a plan view showing a first modification of the radiationplate.

FIG. 17 is a plan view showing a second modification of the radiationplate.

FIG. 18 is a plan view showing a third modification of the radiationplate.

FIGS. 19A and 19B include diagrams showing a fourth modification of theradiation plate wherein FIG. 19A is an exploded plan view and FIG. 19Bis a plan view in a combined state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Wireless IC devices according to preferred embodiments of the presentinvention will be described below with reference to the drawings. Thesame reference numerals are used to identify parts and components commonto the drawings. A duplicated description of such parts and componentsis omitted herein.

First Preferred Embodiment

The configuration of a wireless IC device of a first preferredembodiment of the present invention will now be described with referenceto FIGS. 1A to 1C. As shown in FIGS. 1A to 1C, in a wireless IC device1, a radiation plate 3 defined by a metallic film, such as a metallicfoil, for example, is provided on a support base 2, which is, forexample, a printed circuit board. A power-supply circuit board 4 ismounted on the radiation plate 3. The power-supply circuit board 4includes a power supply circuit including at least one coil pattern, anda wireless IC chip 5 arranged to process a specific radio signal ismounted on the power-supply circuit board 4. Specifically, the wirelessIC chip 5 is mounted on one main surface 4 a of the power-supply circuitboard 4, and the power-supply circuit board 4 is mounted on theradiation plate 3 with the other main surface 4 b of the power-supplycircuit board 4 defining the mounting surface. The wireless IC chip 5includes a clock circuit, a logic circuit, a memory circuit, and othersuitable circuit elements, and necessary information is stored in thewireless IC chip 5.

As shown in FIG. 1B, multiple connection electrodes 11 via which thewireless IC chip 5 is mounted on and connected to the power-supplycircuit board 4 are provided on the one main surface 4 a of thepower-supply circuit board 4. The connection electrodes 11 areelectrically connected to respective multiple connection electrodes (notshown) provided on the rear surface of the wireless IC chip 5 viaconductive bonds 8 (see, for example, FIG. 10) such as solder, forexample. As a result, the wireless IC chip 5 is mounted on the one mainsurface 4 a of the power-supply circuit board 4. In addition, mountingelectrodes 12 via which the power-supply circuit board 4 is mounted onthe radiation plate 3 are provided on the other main surface 4 b of thepower-supply circuit board 4.

As shown in FIG. 1C, the radiation plate 3 includes an opening 7provided in a portion thereof and a slit 6 connected to the opening 7.One end of the slit is connected to the opening 7 and the other endthereof opens at a side edge of the radiation plate 3. In other words,the slit 6 is arranged so as to communicate the opening 7 with the sideedge of the radiation plate 3. Although the slit 6 preferably has asubstantially straight shape, as in the first preferred embodiment, interms of the workability, the slit 6 may have a meandering shape or acurved shaped.

Furthermore, multiple mounting electrodes 15 via which the power-supplycircuit board 4 is mounted on and connected to the periphery of theopening 7 are provided on the radiation plate 3. The mounting electrodes15 are preferably connected to the mounting electrodes 12 provided onthe other main surface 4 b of the power-supply circuit board 4 viaconductive bonds 16, such as solder, for example (see, for example, FIG.5A). The mounting electrodes 15 are preferably defined by aperturesresulting from partially striping a protective layer 14 that is coatedon the surface of the radiation plate 3 and that is made of a resistmaterial or other suitable material, for example. In other words, aportion of the radiation plate 3, which corresponds to the open portionsin the protective layer 14, defines the mounting electrodes 15.

In the first preferred embodiment, the mounting electrodes 12 providedon the other main surface 4 b of the power-supply circuit board 4 arepreferably not directly connected to the power supply circuit providedinside the power-supply circuit board 4. The mounting electrodes 12 arepreferably connected to the mounting electrodes 15 defined by a portionof the radiation plate 3 via the conductive bonds 16, such as solder.

The radiation plate 3 preferably has a substantially planar rectangularshape, for example, as shown in FIG. 2, and the power-supply circuitboard 4 on which the wireless IC chip 5 is mounted is mounted at asubstantially central portion near one longitudinal side edge of theradiation plate 3. In the first preferred embodiment, for example, aground electrode that is incorporated in an electronic device, such as amobile phone or a personal computer, and that is provided on a printedcircuit board including a certain electronic circuit may be used as theradiation plate 3. In other words, although the radiation plate 3 may beprovided as a separate element having only a radiation function, groundelectrodes used in various electronic circuits may alternatively be usedas the radiation plate 3.

In relation to a coil pattern 23, shown in FIG. 3, provided in thepower-supply circuit board 4, the opening 7 provided in the radiationplate 3 overlaps with at least a portion of an inner area of the windingpath of the coil pattern 23, when viewed in plan from the direction ofthe winding axis of the coil pattern 23. As shown in FIG. 3, the opening7 preferably substantially entirely overlaps with the inner area of thecoil pattern 23 and the opening 7 preferably has approximately the samearea as that of the inner area of the coil pattern 23. This is becausemagnetic fields H, shown in FIG. 5A, caused by the coil pattern 23efficiently spread over the radiation plate 3 to suppress loss andimprove the gain.

The power-supply circuit board 4 in the first preferred embodimentincludes a multilayer body in which a plurality of dielectric layerspreferably defined by resin layers or ceramic layers, for example, arelayered. Preferably, the coil pattern 23 of the power supply circuitincludes a plurality of annular electrodes arranged on the plurality ofdielectric layers that are connected to one another via interlayerconductors in the layered direction in a helical pattern having thewinding axis. However, the power-supply circuit board may include a coilpattern provided on a single-layer board.

As shown in FIG. 4, the power-supply circuit board 4 including thehelical coil pattern 23 supplies a transmission signal from the wirelessIC chip 5 to the radiation plate 3 and supplies a reception signal fromthe radiation plate 3 to the wireless IC chip 5.

The power supply circuit will now be specifically described. Aconnection electrode 11 a arranged to be connected to the connectionelectrode on the wireless IC chip 5 is connected to a pad conductor 22 aprovided on another layer via an interlayer connection conductor 21 aprovided in the multilayer body, and a wiring conductor 23 a thatextends from the pad conductor 22 a and that defines a portion of thecoil pattern 23 on the corresponding layer is arranged in asubstantially annular shape to be connected to a pad conductor 24 aprovided on the same layer. The pad conductor 24 a is connected to a padconductor 22 b provided on another layer via an interlayer connectionconductor 21 b, and a wiring conductor 23 b that extends from the padconductor 22 b and that defines a portion of the coil pattern 23 on thecorresponding layer is arranged in a substantially annular pattern to beconnected to a pad conductor 24 b provided on the same layer.

Furthermore, the pad conductor 24 b is connected to a pad conductor 22 cprovided on another layer via an interlayer connection conductor 21 c,and a wiring conductor 23 c that extends from the pad conductor 22 c andthat defines a portion of the coil pattern 23 on the corresponding layeris arranged in a substantially annular pattern to be connected to a padconductor 24 c provided on the same layer. The pad conductor 24 c isconnected to a pad conductor 22 d provided on another layer via aninterlayer connection conductor 21 d, and a wiring conductor 23 d thatextends from the pad conductor 22 d and that defines a portion of thecoil pattern 23 on the corresponding layer is routed in an annularpattern to be connected to a pad conductor 24 d provided on the samelayer.

Furthermore, the pad conductor 24 d is connected to a pad conductor 22 eprovided on another layer via an interlayer connection conductor 21 e,and a wiring conductor 23 e that extends from the pad conductor 22 e andthat defines a portion of the coil pattern 23 on the corresponding layeris arranged in a substantially annular pattern to be connected to a padconductor 24 e provided on the same layer. The pad conductor 24 e isconnected to a pad conductor 22 f provided on another layer via aninterlayer connection conductor 21 f, and a wiring conductor 23 f thatextends from the pad conductor 22 f and that defines a portion of thecoil pattern 23 on the corresponding layer is arranged in asubstantially annular pattern to be connected to a pad conductor 24 fprovided on the same layer. The pad conductor 24 f is connected to aconnection electrode 11 b via an interlayer connection conductor 25.

In other words, the interlayer connection conductors 21 a to 21 f, thepad conductors 22 a to 22 f, the substantially annular wiring conductors23 a to 23 f, the pad conductors 24 a to 24 f, and the interlayerconnection conductor 25 define the coil pattern 23. Electrodes 11 c and11 d are provided on the surface of the multilayer body defining thepower-supply circuit board 4. The electrodes 11 c and 11 d function asmounting electrodes to mount the wireless IC chip 5 and are notconnected to the coil pattern 23 provided in the power-supply circuitboard 4.

As described above, in the first preferred embodiment, the radiationplate 3 includes the opening 7 provided in a portion thereof and theslit 6 connected to the opening 7. The opening 7 overlaps with the innerarea of the coil pattern 23, when viewed in plan from the direction ofthe winding axis of the coil pattern 23 provided in the power-supplycircuit board 4. In addition, the opening 7 preferably has approximatelythe same area as that of the inner area of the coil pattern 23.Accordingly, as shown in FIG. 5A, for example, during the transmissionof a radio signal, a signal current flows from the wireless IC chip 5 tothe coil pattern 23 and the induced magnetic fields H caused by thecurrent is ideally distributed through the opening 7, as shown by brokenlines in FIG. 5A. The ideal distribution of the magnetic fields H meansthat a center B of the two magnetic fields H coincides with the centerof the opening 7. The gain of the radiation plate 3 is maximized in thisstate.

The induced magnetic fields H cause induced currents I1 and I2 (thepropagation direction of the current I1 differs from that of the currentI2 by 180 degrees) around the opening 7, as shown in FIG. 5B. Since theslit 6 is connected to the opening 7, the flows of the induced currentsI1 and I2 are restricted by the slit 6 to produce a difference involtage, i.e., to produce a capacitance. Accordingly, the amounts and/ordistributions of the induced currents I1 and I2 can be effectivelycontrolled by adjusting a length L1 and/or a width L2 of the slit 6 tocontrol the amounts of the electric field and the magnetic fieldproduced over the radiation plate 3. As a result, it is possible toeffectively control the gain of the transmission signal.

In the radiation plate 3, the distribution of the electromagnetic fieldis two-dimensionally spread over the radiation plate 3 due to a linkageamong the induction of the magnetic fields H by the induced currents I1and I2, the induction of an electric field E by the magnetic fields H,and the induction of the magnetic fields H by the electric field E, asshown in FIG. 5C. The distribution of the electromagnetic field producesthe transmission of the radio signal. Accordingly, it is preferable thatthe radio signal processed in the wireless IC device 1 be within a highfrequency band, and more preferably, within a ultra high frequency (UHF)band.

As described above, the gain of the radio signal transmitted andreceived on the radiation plate 3 can be controlled by adjusting thelength L1 and/or the width L2 of the slit 6. Specifically, the gaintends to increase when the length L1 of the slit 6 is increased and whenthe width L2 of the slit 6 is decreased.

As shown in FIG. 5A, it is preferable that the main portions of themounting electrodes 12 provided on the power-supply circuit board 4 beprovided in areas other than the inner area of the coil pattern 23, whenviewed in plan from the direction of the winding axis of the coilpattern 23. In other words, it is preferable that the mountingelectrodes 12 be arranged so as not to impede the production of theideal magnetic fields H, particularly, so as not to impede the magneticfields H passing through the opening 7. Furthermore, it is preferablethat the main portions of the mounting electrodes 12 be provided withinthe plane of incidence of the coil pattern 23. Similarly, when viewed inplan from the direction of the winding axis of the coil pattern 23, themain portions of the mounting electrodes 15 toward the radiation plate 3are preferably provided in areas other than the inner area of the coilpattern 23 and, furthermore, the main portions of the mountingelectrodes 15 are preferably provided within the plane of incidence ofthe coil pattern 23.

As shown in FIG. 4 and FIG. 5A, the substantially annular wiringconductors 23 b to 23 f provided on the respective dielectric layerspreferably include a plurality of line conductors that are parallel orsubstantially parallel with each other at predetermined intervals.Specifically, in the first preferred embodiment, the substantiallyannual-shaped wiring conductors 23 b to 23 f include two line conductorsthat are parallel or substantially parallel with each other and thatconnects the pad conductors arranged at both sides. Consequently, themagnetic flux passes between the two line conductors so to spread theexcited magnetic fields toward the center of the coil pattern 23, thatis, in a direction perpendicular or substantially perpendicular to thewinding axis, thus allowing the magnetic flux to be efficiently used. Inaddition, an increase in the number of the annular conductors that areparallel or substantially parallel with each other has the advantage ofdecreasing the direct current resistance of the annular conductors. As aresult, the gain of the radio signal is improved.

As shown in FIG. 6, the wireless IC device 1 of the first preferredembodiment includes a differential-output-type wireless IC chip 5 and isconfigured such that the coil pattern 23 is connected in series betweentwo input-output electrodes. And, the induced magnetic fields H inducedby the coil pattern 23 are propagated to the portion around and throughthe opening 7 of the radiation plate 3 in an ideal manner.

Although only the coil pattern 23 is shown as the power supply circuitin this equivalent circuit, the stray capacitance produced between theannular electrodes on the respective layers is also used as acapacitance component because the inductance of the coil pattern 23 isused as an inductance component and the coil pattern 23 is defined bythe layered annular electrodes, as described above. It is sufficient forthe power supply circuit provided in the power-supply circuit board 4 toinclude at least the coil pattern. If the power supply circuit has aparticular resonant frequency, the power supply circuit may preferablyfurther include, for example, a capacitance component and an inductancecomponent arranged to adjust the resonant frequency.

In the first preferred embodiment, the power supply circuit in thepower-supply circuit board 4 preferably has a particular resonantfrequency and the frequency of the radio signal transmitted and receivedon the radiation plate 3 preferably substantially corresponds to theresonant frequency. The “substantial correspondence” means that thebandwidth of the resonant frequency of the power supply circuit issubstantially the same as the frequency band of the radio signals thatare transmitted and received on the radiation plate 3. Since thefrequencies of the transmission signal and/or the reception signal aresubstantially the same as the resonant frequency of the power supplycircuit, as described above, it is possible to provide a wireless ICdevice having stable frequency characteristics that do not depend on thesize and/or shape of the radiation plate 3 or the shape, the material,or other characteristics of the support base 2 which supports theradiation plate 3.

In the first preferred embodiment, as shown in FIG. 7, in terms of thearea of the periphery of the opening 7 in the radiation plate 3, thatis, the area of the portion in which the magnetic flux induced by thecoil pattern 23 is received, it is preferable that T2>T1 where T1denotes the thickness of the coil pattern 23 in the layering directionand T2 denotes the length from a position 10 a corresponding to theouter edge of the coil pattern 23 to an outer edge 10 b of the radiationplate 3. Establishing such a relationship between the size of theperiphery of the opening 7 in the radiation plate 3 and the size of thecoil pattern 23 enables the magnetic flux caused by the coil pattern 23to be received at the side of the radiation plate 3 at a high efficiencyof at least about 80%, thus providing a wireless IC device having areduced loss and greater gain.

Since the power-supply circuit board 4 is coupled to the radiation plate3 primarily via the magnetic field in the first preferred embodiment, itis not necessary to consider the impedance matching between thepower-supply circuit board 4 and the radiation plate 3. In other words,according to the first preferred embodiment, as described above,preferably designing the shape of the slit 6 enables the gain of theradio signal to be very easily controlled.

Second Preferred Embodiment

As shown in FIG. 8A, a wireless IC device 31 of a second preferredembodiment of the present invention is similar to the wireless IC device1 of the first preferred embodiment. The wireless IC device 31 of thesecond preferred embodiment differs from the wireless IC device 1 of thefirst preferred embodiment in that a power-supply circuit board 34 isarranged along a side edge of a radiation plate 33. In the wireless ICdevice 31, the length, refer to as L1 in FIG. 5B, of a slit 36 extendingfrom the side edge of the radiation plate 33 to an opening 37 isdecreased and, thus, the gain tends to be decreased. In addition, asshown in FIG. 8B, the width of a slit 36′ provided in a radiation plate33′ may be approximately the same as the width of an opening 37′.

Specific numerical values of the gain depending on the numerical valueof the length L1 of the slit 36 will now be described when the radiationplate 33 has a length of about 14 cm and a width of about 4 cm.

When L1=about 0 mm, the gain is equal to about −14.4 dB.

When L1=about 0.5 mm, the gain is equal to about −13.1 dB.

When L1=about 1.0 mm, the gain is equal to about −11.6 dB.

When L1=about 1.5 mm, the gain is equal to about −10.9 dB.

When L1=about 2.5 mm, the gain is equal to about −9.4 dB.

When L1=about 4.5 mm, the gain is equal to about −7.9 dB.

In the coil pattern 23 provided in the power-supply circuit board 4, theannual conductor provided on each dielectric layer may include one lineconductor, as shown in FIG. 9. The coil pattern 23 shown in FIG. 4includes the wiring conductors 23 b to 23 f provided on the five layerswhereas the coil pattern 23 shown in FIG. 9 includes the coil patterns23 b to 23 e provided on the four layers.

When each of the annual conductors (the wiring conductors 23 b to 23 e)provided on the respective dielectric layers includes one lineconductor, as in this modification, the amount of the two-dimensionaldistribution of the induced magnetic fields caused by the coil pattern23 is decreased and, thus, the gain tends to be decreased as compared tothe configuration shown in FIG. 4. However, the configuration shown inFIG. 9 is simplified and the size of the power-supply circuit board 4can be reduced.

Third Preferred Embodiment

A wireless IC device 61 of a third preferred embodiment of the presentinvention differs from the wireless IC device 1 of the first preferredembodiment in that a radiation plate 63 is provided inside a supportbase 62, as shown in FIG. 10. In other words, ground electrodes providedinside the support base 62, for example, a printed circuit board, areused as the radiation plate 63.

Specifically, as shown in FIG. 10, in the wireless IC device 61, theradiation plate 63 including an opening 67 to which a slit (not shown)is connected is provided inside the support base 62. In addition, thepower-supply circuit board 4 is mounted on the support base 62. Thepower-supply circuit board 4 includes a power supply circuit includingthe coil pattern 23. Furthermore, the wireless IC chip 5 arranged toprocess a specific radio signal is mounted on the surface of thepower-supply circuit board 4.

Mounting electrodes 68 arranged to mount the power-supply circuit board4 are provided on the surface of the support base 62. The mountingelectrodes 68 are connected to the mounting electrodes 12 provided onthe other main surface 4 b of the power-supply circuit board 4 via theconductive bonds 16, such as solder, for example. In addition, themounting electrodes 12 on the power supply circuit board 14 are notdirectly connected to the power supply circuit provided inside thepower-supply circuit board 4. Similarly, the mounting electrodes 68 onthe support base 62 are not directly connected to the radiation plate 63provided inside the support base 62.

Fourth Preferred Embodiment

A wireless IC device 71 of a fourth preferred embodiment of the presentinvention is a tag-type (inlay-type) wireless IC device, as shown inFIG. 11. Specifically, the wireless IC device 71 includes a radiationplate 73 preferably defined by a flexible metallic film, such as ametallic foil, for example, that is provided on a flexible support 72,such as a polyethylene terephthalate (PET) film, for example. Theradiation plate 73 includes a peripheral portion of an opening 77 towhich a slit 76 is connected, that is, a substantially planar portion 78in which the magnetic flux induced by the coil pattern in thepower-supply circuit board is received and meandering portions 79 inwhich a radio signal is primarily transmitted and received. However, noclear boundary is provided between the planar portion 78 in which themagnetic flux is received and the meandering portions 79 in which theradio signal is transmitted and received. As in the wireless IC device 1of the first preferred embodiment, mounting electrodes 75 via which thepower-supply circuit board is mounted are provided around the opening 77by partially striping a resist material. The wireless IC device 71 canpreferably be attached to various commercial products and can be usedfor management of distribution histories of the commercial products.

As described above, in the wireless IC devices according to preferredembodiments of the present invention, the support which supports theradiation plate may be not only a rigid board, such as a printed circuitboard, for example, but may also be a flexible support 72 such as a PETfilm, for example, as described in the fourth preferred embodiment.Similarly, the radiation plate itself may be not only a rigid plate,such as a sintered metal or a metal plate, for example, but also aflexible plate, such as a metallic foil, for example. In addition, aportion of a metal article, such as a metallic frame of a pair ofglasses or a ring, for example, may be used as the radiation plate.

Fifth Preferred Embodiment

In a wireless IC device 81 of a fifth preferred embodiment of thepresent invention, a radiation plate 83 defined by a metallic foil orother suitable material, for example, is provided on a relatively smallsupport 82 defined by a flexible film or other suitable material, asshown in FIG. 12. The wireless IC device 81 preferably has a patchshape, for example. The radiation plate 83 includes an opening 87 and aslit 86 connected to the opening 87.

As shown in FIG. 13, the wireless IC device 81 is preferably used in astate in which the support 82 is adhered on an article 89. If thesupport 82 has a thickness that allows the magnetic flux to passtherethrough, the article may preferably be made of metal.

Sixth Preferred Embodiment

In a wireless IC device 91 of a sixth preferred embodiment of thepresent invention, mounting electrodes 12 a and 12 b connected to thecoil pattern 23 via interlayer connection conductors 26 a and 26 b areprovided on the rear surface of the power-supply circuit board 4 and themounting electrodes 12 a and 12 b are connected to mounting electrodes15 a and 15 b on the radiation plate 3 via the conductive bonds 16, suchas solder, for example, as shown in FIGS. 14 and 15. The mountingelectrodes 15 a and 15 b are defined by apertures resulting frompartially striping a resist material coated on the surface of theradiation plate 3, as in the mounting electrodes 15 described in thefirst preferred embodiment. The configuration of the wireless IC device91 is otherwise substantially the same as that of the first preferredembodiment.

In other words, in the sixth preferred embodiment, not only the coilpattern 23 in the power-supply circuit board 4 is electromagneticallycoupled to the radiation plate 3, but also the coil pattern 23 in thepower-supply circuit board 4 is directly connected (coupled) to theradiation plate 3. Accordingly, the gain of the radiation plate 3 isincreased.

Meanwhile, if a plurality of wireless IC devices that have substantiallythe same configuration and that each include a relatively largeradiation plate are laid over one another, the radiation plates tend toblock the magnetic flux. In such a state, the transmission and receptionbetween the wireless IC devices and a reader-writer is disabled.Accordingly, first to fourth modifications of the radiation plate whichincludes an aperture so that the magnetic flux can pass through thewireless IC devices even if the plurality of wireless IC devices arelaid over one another are shown in FIGS. 16 to 19. The arrangements ofthe apertures shown in the first to fourth modifications in theradiation plates enable the magnetic flux to pass through the apertureeven when a plurality of wireless IC devices are laid over one another,thus enabling communication with the reader-writer. In addition, thepresence of the annular electrodes increases the area of a portion wherethe magnetic flux is received on the radiation plate to improve the gainas an antenna.

A radiation plate 100 of a first modification, shown in FIG. 16,includes a first electrode 101 including an opening 107 over which thepower-supply circuit board 4 is mounted and a slit 106, and an annularsecond electrode 108 surrounding the first electrode 101. The radiationplate 100 is preferably defined by a metallic foil or other suitablematerial, for example. The first and second electrodes 101 and 108 areintegrally provided on one plane and are electrically connected to eachother via a connection portion 102. In the first modification, themagnetic flux passes through an aperture 109 surrounded by the annularsecond electrode 108. It is preferable that the opening 107 over whichthe power-supply circuit board 4 is mounted is arranged at a centralportion of the annular second electrode 108. This configuration enablesthe power-supply circuit board 4 to evenly receive the magnetic flux.

A radiation plate 110 of a second modification, shown in FIG. 17,includes a first electrode 111 including an opening 117 over which thepower-supply circuit board 4 is mounted and a slit 116, and an annularsecond electrode 118 surrounding the first electrode 111. The radiationplate 110 is preferably defined by a metallic foil or other suitablematerial, for example. The first and second electrodes 111 and 118 areintegrally provided on one plane and are electrically connected to eachother via connection portions 112 and 113. Since the first electrode 111is connected to the annular second electrode 118 at two positions, asdescribed above, an electrical signal caused by the magnetic field isefficiency transmitted to the power-supply circuit board 4. In thesecond modification, the magnetic flux passes through apertures 119surrounded by the annular second electrode 118.

A radiation plate 120 of a third modification, shown in FIG. 18,includes a first electrode 121 including an opening 127 over which thepower-supply circuit board 4 is mounted and a slit 126, and an annularsecond electrode 128 surrounding the first electrode 121. The first andsecond electrodes 121 and 128 are integrally provided on one plane andare electrically connected to each other via a connection portion 122.In the third modification, the magnetic flux passes through apertures129 surrounded by the annular second electrode 128.

In a radiation plate 130 of a fourth modification, shown in FIG. 19, afirst electrode 131 is provided separately from a second electrode 138and the first electrode 131 is adhered on the second electrode 138.Either of a non-conductive adhesive and a conductive adhesive, forexample, may preferably be used for the adhesion. In addition, the firstelectrode 131 may be adhered on the second electrode 138 so that thefirst electrode 131 opposes the second electrode 138 or so that the filmhaving the first electrode 131 provided on its surface opposes thesecond electrode 138. The magnetic field is propagated even if theelectrode 131 is adhered on the electrode 138. The first electrode 131includes an opening 137 over which the power-supply circuit board 4 ismounted and a slit 136. The second electrode 138 has the same orsubstantially the same shape as in the second modification. The magneticflux passes through apertures 139 surrounded by the second electrode138. In the fourth modification, making the opening and the slit in thesecond electrode 138 larger than the opening 137 and the slit 136 in thefirst electrode 131 enables the opening 137 of a predetermined size andthe width of the slit 136 to be ensured in the first electrode 131 evenif a slight positional shift occurs in the adhesion of the firstelectrode 131 on the second electrode 138.

The wireless IC devices according to preferred embodiments of thepresent invention are not restricted to the preferred embodimentsdescribed above and may be varied within the scope of the summary of thepresent invention.

As described above, preferred embodiments of the present invention areuseful for a wireless IC device and, particularly, are excellent in thatthe gains of transmission and reception signals can be effectivelycontrolled.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A wireless integrated circuit device comprising:a wireless integrated circuit configured to process a radio signal; apower-supply circuit connected to the wireless integrated circuit andincluding a coil pattern; and a planar-shaped radiation plate configuredto radiate a transmission signal supplied from the power-supply circuitor to receive a reception signal to supply the reception signal to thepower-supply circuit; wherein the planar-shaped radiation plate is aground electrode and includes an opening; the coil pattern ismagnetically coupled to the planar-shaped radiation plate; and at leasta portion of an inner area of the coil pattern overlaps the opening ofthe planar-shaped radiation plate.
 2. The wireless integrated circuitdevice according to claim 1, wherein at least a portion of an inner areaof the coil pattern does not overlap the planar-shaped radiation plate.3. The wireless integrated circuit device according to claim 1, whereinthe planar-shaped radiation plate is provided in a printed circuitboard; and the wireless integrated circuit is a chip type wirelessintegrated circuit and is mounted on one main surface of the printedcircuit board.
 4. The wireless integrated circuit device according toclaim 1, wherein the power-supply circuit is defined by a multilayerbody including a plurality of layered dielectric layers, and a pluralityof annular conductors are arranged on the plurality of dielectric layersand connected to one another via interlayer conductors extending in alayering direction of the multilayer body so as to define a helicalpattern.
 5. The wireless integrated circuit device according to claim 4,wherein each of the plurality of annular conductors provided on theplurality of dielectric layers includes a plurality of line conductorsthat are arranged at predetermined intervals and that are parallel orsubstantially parallel with each other.
 6. The wireless integratedcircuit device according to claim 1, wherein the power supply circuithas a resonant frequency and the frequencies of at least one of thetransmission signal and the reception signal substantially correspond tothe resonant frequency.